Geoscience Reference
In-Depth Information
Figure 5.3 Gradient from coast to higher elevations in Mesoamerican Tropical Sea-
sonal Forests.
(Illustration by Jeff Dixon. Adapted from Robichaux and Yetman 2000.)
inceptisols dominate have been cleared and converted for agriculture. Well-drained
fertile entisols and alfisols are extensively used for agricultural production.
Although seasonality of rainfall is the dominant influence on the biome, soil
type can affect forest structure and composition. More drought-resistant evergreen
vegetation is found on the more infertile soils, while lush deciduous vegetation is
found on the fertile and deeper soils. Soil erosion is high when the forest is con-
verted for other uses. Rates of soil formation are low, leading to little recovery of
these tropical soils once they are disturbed.
Vegetation in the Neotropical Seasonal Forests
As in other regions, the Neotropical Seasonal Forest Biome includes several types
of forest. The semi-evergreen and moist deciduous forests are found along the pe-
rimeter of lowland rainforests, and as latitude increases the forest becomes drier
with dry evergreen forests dominating. In drier subtropical areas or at higher eleva-
tions, thorn forests and oak-pine forests start to emerge (see Figure 5.3)
Forest Structure
Seasonal forests are varied in the Neotropics, and most seasonal forests tend to be
of smaller stature and simpler structure than the rainforest. However, the range in
forest structure is considerable due to geography, soils, and duration and intensity
of the dry season. In addition to seasonal resource availability, structure plays a
role in creating a variety of microhabitats within the forests.
In the tropical moist deciduous forests, a complex four- to five-layered forest is
present (see Figure 5.4). The top layer consists of widely spaced deciduous trees
